In the current cloud computation, servers that provide cloud services with computation and storage capabilities are all arranged in the data center and are connected via networks. Therefore, the role of the today's data center is becoming increasingly important.
FIG. 1 is a schematic diagram for illustrating a structure of a typical data center network. In a tree network structure as shown in FIG. 1, an edge switch (or ToR) usually has forty-eight 1G Ethernet ports downwardly connected to servers and one to four 10G Ethernet ports upwardly connected to aggregation switches. A link between an edge switch and an aggregation switch is referred to as uplink. Thus, when there are a large number of data communications occurring for servers between Racks, the core network will often become a bottleneck, which results in degradation of applications' performances. Especially in today's cloud computation environments, a growing number of applications like Map-Reduce require transferring large amounts of data between the servers. One simple optimization method is to localize as many servers' communications as possible, i.e., data transmission does not need to go through the core network. Imagine if a rack is capable of accommodating a sufficient number of servers, so that a large distributed system can be completely deployed over these services and thus communications between these servers do not need to go through the congested core network, then the core network will not become the bottleneck of the system. In reality, however, the number of connectable servers in one rack is limited to the number of ports of an edge switch (usually 48). It is of very high cost to extend the number of ports of the edge switch, for example, the price of a 96-port switch is about ten times that of a 48-port switch.
FIG. 2 is a schematic diagram for illustrating a combination of an edge switch stack solution and a server end link aggregation solution. The benefit of such a connection is to increase bandwidth of servers, and communications of servers under each edge switch and is not limited to stacked data lines. According to the edge switch stack solution, the edge switch may be equipped with extra stack modules, and may be connected with each other via data lines (data lines “2 to 2.5G” as shown in FIG. 2). In accordance with the server end link aggregation (Link Aggregation, or Network Interface Card (NIC) Bonding) solution, a plurality of NICs are inserted into one server (host), and software providing a link aggregation function may allow a plurality of NICs to share one network identifier (e.g., a MAC address, an IP address, and the like). However, even if the edge switch stack solution is combined with the server end link aggregation solution, the number of servers capable of direct communication does not increase. For example, assume each switch has 48 ports, then the number of servers that are connected in such a combination is still (48+48)/2=48, because each server needs to occupy two ports of the switch.